1. Field of the Invention
The present invention relates generally to a self-elevating drilling or maintenance platform, and more particularly to a device for temporarily supporting such a platform to permit in situ maintenance on its jacking components.
2. Description of the Related Art
Drilling platforms are commonly used for offshore exploration and extraction of petroleum products from beneath the seabed.
One type of such platform is supported by legs that are lowered by a jacking system into the seabed. After the platform is elevated above the water, it is held in position by the jacking system to form a stable drilling platform. It is difficult to maintain the jacks and associated equipment, especially in older types of such platforms, without taking the platform out of service and towing it to a drydock. It would be preferable to support the platform in situ for such maintenance.
Examples of drilling platforms that include platform-supporting structure are shown in U.S. Pat. Nos. 3,343,371, 4,269,543, 4,389,140, 4,538,938, 4,627,768, 5,092,712, 5,139,366, 5,188,484, 5,486,069, 5,611,645, 5,622,452 and 6,076,996. However, none of them solve the problem of permitting maintenance of a drilling platform""s jacking system and associated parts when the platform has no way of supporting itself other than the jacking system.
It is an object of the present invention to overcome the problems of the prior art by using a support device that can support a drilling platform in situ.
In accordance with one aspect of the invention, a support device for a drilling platform supported by at least one leg including a jacking rack with jacking teeth for meshing with a jacking mechanism for raising and lowering the platform comprises a rack chock having a portion with at least one locking tooth for meshing with the jacking teeth on the jacking rack and a support seat for engaging the platform, a clamping portion attachable to the rack chock, and removable fasteners for securing the clamping portion to the rack chock to hold the rack chock in place on the leg with the locking tooth meshed with at least one of the jacking teeth on the jacking rack.
In accordance with another aspect of the invention, a drilling or maintenance platform comprises a plurality of legs supporting the platform in an operating orientation, each leg including a jacking rack with jacking teeth, a plurality of jacking mechanisms associated with the legs for meshing with the jacking teeth to raise and lower the platform, and a plurality of support devices for supporting the platform independent of the jacking mechanisms, each device including (i) a rack chock having a portion with at least one locking tooth for meshing with the jacking teeth of an associated leg and a support seat for engaging the platform, (ii) a clamping portion attachable to the rack chock, and (iii) removable fasteners for -securing the clamping portion to the rack chock to hold the rack chock in place on the leg with the locking tooth meshed with at least one of the jacking teeth.
In accordance with yet another aspect of the invention, a method of temporarily supporting a self-elevating drilling platform supported in an operating orientation by a plurality of legs, each including a jacking rack with jacking teeth for meshing with a jacking system for raising and lowering the platform comprises providing a like plurality of rack chocks, each having a portion with at least one locking tooth meshed with the jacking teeth, a support seat for engaging the platform, and a clamping portion attachable to the rack chock, using removable fasteners to secure each clamping portion to an associated rack chock with the locking tooth thereof meshed with at least one of the jacking teeth of the associated leg so that the support seat is beneath a hull portion of the platform, lowering the platform relative to the legs so that the hull portion rests on the support seats, and disengaging the jacking mechanism from the jacking teeth.